Flat display panels for displaying characters or messages have been known for some time, both in single register and multi-register form. In addition, there has been an ever-present need for large display panels of wall size; however, panels of this size have not been obtainable commercially. An alternative to making a single panel of large size is to make smaller panel modules and to couple together such panel modules to form a total large-area panel. However, suitable panel modules have not been available for this purpose.